Large diameter porous plug and two-step soft chuck method for argon delivery.

Abstract

The present disclosure relates to a substrate support assembly for reducing pumping time when using argon gas. In one embodiment, the substrate support assembly includes a porous plug therein. The porous plug includes a first cylindrical section having a first volume and an axial length and a second cylindrical section having a second volume and an axial length. The first cylindrical section has a larger volume than the second cylindrical section. The first cylindrical section and the second cylindrical section have a volume ratio of about 2 to about 12. The axial length of the first cylindrical section and the axial length of the second cylindrical section have a length ratio of about 2 to about 10.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 412,271, filed September 30, 2022, the entire contents of which are incorporated herein by reference.

[0002]

[0002] Embodiments of the present invention relate generally to semiconductor processing and manufacturing. In semiconductor processing, plasma processes are often performed in a vacuum by evacuating gases from the processing chamber. In such processes, a substrate is placed on an electrostatic chuck (ESC) disposed on a stage of the processing chamber. The electrostatic chuck includes a conductive sheet-type chuck electrode disposed between dielectric members (e.g., dielectric layers). [Background technology]

[0003]

[0003] Helium is a commonly used backside gas in semiconductor processing. However, helium is expensive, and the use of such gas increases the cost of processing substrates. Furthermore, when the chucking voltage of an electrostatic chuck is increased, the resulting forces when helium is used can cause additional vacuum leakage due to the small atomic size of helium. Therefore, the use of helium as a backside gas can cause pressure and vacuum instabilities within the process chamber.

[0004] Therefore, there is a need for an apparatus and method for improving backside gas processing during semiconductor processing.

[0005] In semiconductor processing, plasma processes are often performed in a vacuum by evacuating gases from the processing chamber. In such processes, a substrate is placed on an electrostatic chuck (ESC) located on a stage of the processing chamber. The ESC includes a conductive sheet-type chuck electrode disposed between dielectric members (e.g., dielectric layers).

[0006]

[0006] When performing a plasma process, a voltage from a DC voltage source is applied to the chucking electrode from the voltage source, and the substrate is "chucked" to the surface of the electrostatic chuck by Coulomb or Johnson-Rahbek forces resulting from the applied voltage. Once the plasma process is completed, the voltage applied to the chucking electrode of the electrostatic chuck is typically turned off or set to a low value to compensate for any residual charge remaining on the wafer so that the substrate can be dechucked from the electrostatic chuck.

[0007] In one embodiment, to dechuck the substrate, a discharge process is performed in which an inert gas is introduced into the processing chamber to maintain the pressure in the processing chamber at a predetermined pressure level, a voltage of opposite polarity to the voltage applied to the electrostatic chuck during the plasma process is applied, and then the applied voltage is turned off or set to a low value to compensate for any residual charge remaining on the wafer so that the charge on the electrostatic chuck and substrate can be discharged. The support pins are then raised to lift the substrate from the electrostatic chuck and dechuck it.

[0008] During the process of "chucking" a substrate, when a high voltage is applied to the chucking electrode to chuck the substrate to the ESC, the sudden application of the voltage can generate very large forces on the substrate. Furthermore, as the temperature of the substrate equilibrates with the temperature of the electrostatic chuck surface, relative motion occurs between the backside of the substrate and the electrostatic chuck surface due to the mismatch in the coefficients of thermal expansion (CTE) of the substrate and the electrostatic chuck surface. This relative motion between the two components, in turn, causes a relative sliding motion, which has been found to generate particles on the backside of the substrate and / or cause scratches and damage to the backside of the substrate.

[0009]

[0009] Therefore, there is a need for an improved method for reducing the detrimental effects on a substrate when chucking and dechucking the substrate from an ESC. Summary of the Invention

[0010] In one embodiment, a substrate support assembly includes a porous plug therein. The porous plug includes a first cylindrical section having a first volume and an axial length and a second cylindrical section having a second volume and an axial length. The first cylindrical section has a larger volume than the second cylindrical section. The first cylindrical section and the second cylindrical section have a volume ratio of about 2 to about 12. The axial length of the first cylindrical section and the axial length of the second cylindrical section have a length ratio of about 2 to about 10.

[0011] In another embodiment, a processing chamber includes one or more walls surrounding a process region and a substrate support assembly disposed in the process region. The substrate support assembly includes an electrostatic chuck disposed above an insulator plate and a porous plug disposed in the insulator plate. The porous plug includes a porous material, a first cylindrical section having a first volume, a first diameter, and a first axial length, and a second cylindrical section having a second volume smaller than the first volume, a second diameter smaller than the first diameter, and a second axial length smaller than the first axial length.

[0012] In another embodiment, the porous plug includes a cross-linked polystyrene material having uniform porosity, a first cylindrical section having a first volume, a first diameter, and a first axial length, and a second cylindrical section having a second volume smaller than the first volume, a second diameter smaller than the first diameter, and a second axial length smaller than the first axial length. The volume ratio of the volume of the first cylindrical section to the volume of the second cylindrical section is about 2 to about 12. The first cylindrical section is disposed between the second cylindrical section and the process region. The length ratio of the first axial length to the second axial length is about 2 to about 10.

[0013] In another embodiment, a method of chucking a substrate to a surface of an electrostatic chuck (ESC) is provided, the method including applying a first voltage to a chuck electrode of the ESC during a chucking time interval, supplying an inert gas at a first pressure to a backside of the substrate during the chucking time interval, applying a second voltage to the chuck electrode after the chucking time interval that is higher than the first voltage, and supplying an inert gas to the backside of the substrate at a second pressure that is higher than the first pressure of the inert gas after the chucking time interval.

[0014] In another embodiment, a method for dechucking a substrate from a surface of an electrostatic chuck (ESC) is provided, the method including reducing a backside gas pressure on an underside of the substrate, reducing an applied voltage to a chucking electrode of the ESC to a dechucking voltage after the pressure is reduced, increasing the substrate temperature during a dechucking interval, and reducing the backside gas pressure and the dechucking voltage after the dechucking interval.

[0015] In another embodiment, a substrate processing chamber is provided. The chamber includes an electrostatic chuck (ESC) fluidly coupled to a cryogenic cooling system and a controller. The controller includes a central processing unit (CPU), support circuits, and a non-transitory computer-readable medium. The computer-readable medium includes instructions for chucking a substrate. When executed, the instructions cause the ESC to apply a first voltage to a chucking electrode of the ESC for a first time interval, apply an inert gas at a first pressure to a backside of the substrate for the first time interval, apply a second voltage to the chuck electrode for a second time interval after the first time interval, the second voltage being higher than the first voltage, and apply the inert gas at a second pressure to the backside of the substrate for the second time interval, where the second amount of inert gas is less than the first amount of inert gas.

[0016]

[0016] In order that the above-described features of the present disclosure may be understood in detail, the above-summarized disclosure will be more particularly described by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings depict only exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, which may also admit of other equally effective embodiments. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional schematic diagram illustrating a plasma processing chamber according to an embodiment of the present disclosure. [Figure 2] 1 is a cross-sectional schematic diagram illustrating a substrate support assembly according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a cross-sectional schematic diagram illustrating a porous plug in a chamber according to an embodiment of the present disclosure. [Figure 4] 1A and 1B illustrate a method of chucking a substrate. [Figure 5] 1A-1C illustrate a method for dechucking a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0018]

[0022] To facilitate understanding, wherever possible, the same reference numerals have been used to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0019]

[0023] Embodiments described herein provide a substrate support assembly having a porous plug that enables operation of an electrostatic chuck (ESC) using a more economical backside gas than helium so that a substrate disposed on the ESC is maintained at a temperature below −20° C. during substrate processing while other surfaces of the processing chamber are maintained at a different temperature.

[0020]

[0024] Although the substrate support assembly is described below in an etch processing chamber, the substrate support assembly can be utilized in other types of plasma processing chambers, such as physical vapor deposition chambers, chemical vapor deposition chambers, ion implantation chambers, and other systems where processing requires the substrate to be maintained at temperatures below −20° C. The substrate support assemblies disclosed herein can be utilized at temperatures below −20° C.

[0021]

[0025] The use of argon has been found to offer advantages in many substrate processes, including reduced vacuum leakage compared to helium. Additionally, when argon is used as the backside gas, the backside gas velocity into the processing region can be controlled at a substantially constant rate. In contrast, the leak rate of helium into the processing region has been observed to increase with increasing vacuum pressure, potentially resulting in less controllable gas velocity. Because argon has larger molecules than helium, the delivery time of argon gas is longer than that of helium when using the same backside gas delivery system.

[0022]

[0026] The embodiments described herein provide a plug design that allows argon to have a similar backside gas evacuation time as helium, while also retaining the advantages of low leakage in isolation vacuum and low backside gas leakage at high pressures.

[0023]

[0027] FIG. 1 is a schematic cross-sectional view of an exemplary plasma processing chamber 100 configured as an etch chamber having a substrate support assembly 101. The substrate support assembly 101 can be utilized in other types of plasma processing chambers, such as plasma processing chambers, annealing chambers, physical vapor deposition chambers, chemical vapor deposition chambers, and ion implantation chambers, as well as other systems in which the ability to uniformly maintain a surface or workpiece, such as a substrate 124, at a temperature below approximately −20° C. is desirable. The substrate 124 can be subjected to dry reactive ion etching at a variety of temperatures, including temperatures below −20° C. or above 300° C., whereby ions bombard the upward-facing surface of a material disposed on the substrate 124 to form trenches with smooth, vertical sidewalls while reducing spontaneous etching. One of the many advantages of these techniques includes improved etch selectivity of one material over another at temperatures below −20° C. For example, selectivity between silicon (Si) and silicon dioxide (SiO) increases exponentially as temperature decreases.

[0024]

[0028] The plasma processing chamber 100 includes a chamber body 102 having a sidewall 104, a bottom 106, and a lid 108 that surround a process region 110. An injector 112 is coupled to the sidewall 104 and / or the lid 108 of the chamber body 102. A gas panel 114 is coupled to the injector 112 and enables delivery of process gases into the process region 110. The injector 112 may be one or more nozzles or inlet ports, or a showerhead. The process gases, along with any processing by-products, are removed from the process region 110 through exhaust ports 116 formed in the sidewall 104 or bottom 106 of the chamber body 102. The exhaust ports 116 are coupled to a pumping system 140 that includes a throttle valve and a pump that are utilized to control the vacuum level within the process region 110.

[0025]

[0029] A voltage is applied to the process gas to form a plasma in the process region 110. In one embodiment, the process gas is energized by capacitively or inductively coupling RF power or pulsed DC to the process gas. In this embodiment, which can be combined with other embodiments described herein, shown in FIG. 1 , multiple coils 118 are positioned above the lid 108 of the plasma processing chamber 100 and are coupled to an RF power source 122 through a matching network 120.

[0026]

[0030] The substrate support assembly 101 is located in a process region 110 below an implanter 112. The substrate support assembly 101 includes an electrostatic chuck (ESC) 103 and an ESC base 105. The ESC base 105 is coupled to the ESC 103 and an equipment plate 107. The equipment plate 107, supported by a ground plate 111, is configured to facilitate electrical, cooling, heating, and gas connections to the substrate support assembly 101. The ground plate 111 is supported by the bottom 106 of the processing chamber. An insulator plate 109 insulates the equipment plate 107 from the ground plate 111.

[0027]

[0031] The ESC base 105 includes a base channel 115 coupled to a cryogenic chiller 117. The cryogenic chiller 117 is fluidly connected to the base channel 115 via a base inlet conduit 123 connected to the inlet of the base channel 115 and via a base outlet conduit 125 connected to the outlet of the base channel 115 so that the ESC base 105 is maintained at a temperature below −20° C. The cryogenic chiller 117 is coupled to an interface box (not shown) for controlling the flow rate of a base fluid. The base fluid may include a material capable of maintaining a temperature below −50° C. The cryogenic chiller 117 supplies a base fluid that is circulated through the base channel 115 of the ESC base 105. The base fluid flowing through the base channel 115 enables the ESC base 105 to be maintained at a temperature below −20° C., which helps control the lateral temperature profile of the ESC 103 so that a substrate 124 disposed on the ESC 103 is uniformly maintained at a temperature below −20° C. or above 300° C. In one embodiment, which may be combined with other embodiments described herein, the cryogenic chiller 117 is a single-stage chiller operable to maintain the base fluid at a temperature below about −50° C. In another embodiment, which may be combined with other embodiments described herein, the cryogenic chiller 117 is a chiller that utilizes a refrigerant within the chiller to maintain the base fluid at a temperature below −50° C.

[0028]

[0032] The facility plate 107 includes facility channels 113 coupled to a cooling device 119. The cooling device 119 is fluidly connected to the facility plate 107 via a facility inlet conduit 129 so that the facility plate 107 is maintained at a predetermined ambient temperature. The cryogenic cooling device 117 is coupled to an interface box for controlling the flow rate of the facility fluid. The facility fluid may include a material capable of maintaining an ambient temperature of approximately -10°C to approximately 60°C. The cooling device 119 provides the facility fluid that is circulated through the facility plate 107. The facility fluid enables the facility plate 107 to be maintained at a predetermined ambient temperature and helps maintain the insulator plate 109 at a predetermined ambient temperature.

[0029]

[0033] ESC 103 has a support surface 130 and a bottom surface 132 opposite support surface 130. In one embodiment, which can be combined with other embodiments described herein, ESC 103 is made from a ceramic material such as alumina (Al2O3), aluminum nitride (AlN), or other suitable material. Alternatively, ESC 103 can be made from a polymer, such as polyimide, polyetheretherketone, polyaryletherketone, or the like.

[0030]

[0034] The ESC 103 includes a chuck electrode 126 disposed therein. The chuck electrode 126 may be configured as a monopolar electrode, a bipolar electrode, or any other suitable arrangement. The chuck electrode 126 is coupled through an RF filter (not shown) and a fixture plate 107 to a chuck power supply 134 that provides DC power for electrostatically clamping the substrate 124 to a support surface 130 of the ESC 103. The RF filter prevents the RF power utilized to form a plasma (not shown) within the plasma processing chamber 100 from damaging electrical equipment or posing an electrical hazard outside the chamber.

[0031]

[0035] The ESC 103 includes one or more resistive heaters 128 embedded therein. The resistive heaters 128 are utilized to raise the temperature of the ESC 103 as needed to a temperature suitable for processing a substrate 124 disposed on the support surface 130. The resistive heaters 128 are coupled to a heater power supply 136 through a fixture plate 107 and an RF filter (not shown). The RF filter prevents RF power utilized to form a plasma (not shown) within the plasma processing chamber 100 from damaging electrical equipment or posing an electrical hazard outside the chamber. The heater power supply 136 may include a heater controller (not shown) utilized to control operation of the heater power supply 136 and generally configured to heat the substrate 124 as needed to maintain the substrate temperature at a desired temperature. In other embodiments, the controller is separate from the heater power supply 136. In other words, the heat from the resistive heater 128 and the cooling from the base fluid circulating through the ESC base 105 are balanced to maintain the substrate 124 at a desired temperature below −20° C. For example, the resistive heater 128 and the base fluid circulating through the ESC base 105 maintain the substrate 124 at a temperature below about −20° C., such as about −20° C. to about −150° C., suitable for processing.

[0032]

[0036] The resistive heater 128 includes multiple laterally separated heating zones, and the heater controller enables at least one zone of the resistive heater 128 to be preferentially heated relative to resistive heaters 128 located in one or more of the other zones. For example, the resistive heater 128 may be concentrically arranged into multiple separated heating zones. The separated heating zones of the resistive heater 128 aid in controlling temperature uniformity from the lateral edge to the center of the substrate 124. The substrate support assembly 101 may also include one or more probes (not shown) disposed therein. The ESC 103 is coupled to a controller 138. A probe disposed on the ESC base 105 is communicatively coupled to the controller 138 and may be utilized in conjunction with the controller 138 to calibrate the temperature of the substrate based on the temperature of the ESC base 105. The controller 138 is coupled to the heater power supply 136 such that each zone of the resistive heater 128 is heated independently, the lateral temperature profile of the ESC 103 based on temperature measurements is substantially uniform, and the substrate 124 placed on the ESC 103 is maintained uniformly at a temperature below -20°C.

[0033]

[0037] In some embodiments of the present disclosure, an apparatus for chucking and dechucking a substrate from the surface of an ESC of a processing chamber includes a controller 138. The controller 138 includes a programmable central processing unit (CPU) 138A operable with a memory 138B (e.g., non-volatile memory) and support circuits 138C. The CPU 138A of the controller 138 includes one or more processors for executing instructions stored in the memory 138B to implement a method for achieving a two-stage soft chucking process. The support circuits 138C are conventionally coupled to the CPU 138A and include cache, clock circuits, input / output subsystems, power supplies, and combinations thereof coupled to various components of the substrate processing chamber 100 to facilitate its control. The CPU 138A may be any form of general-purpose computer processor used in industrial environments, such as a programmable logic controller (PLC), for controlling the various components and sub-processors of a processing system. The memory 138B coupled to the CPU 138A is a non-transitory computer-readable medium, typically one or more of readily available memory such as random access memory (RAM), read-only memory (ROM), a floppy disk drive, a hard disk, or any other form of digital storage, local or remote.

[0034]

[0038] Typically, memory 138B is in the form of a non-transitory computer-readable storage medium containing instructions (e.g., non-volatile memory) that, when executed by CPU 138A, facilitate operation of chamber 100. The instructions in the memory are in the form of a program product, such as a program that performs the methods of the present disclosure. The program code may conform to any one of a number of different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use with a computer system. The program(s) in the program product define functions of embodiments (including methods described herein).

[0035]

[0039] Exemplary non-transitory computer-readable storage media include, but are not limited to, (i) non-writable storage media on which information may be permanently stored (e.g., a CD-ROM disk readable by a CD-ROM drive, a flash memory, a ROM chip, or any type of solid-state non-volatile semiconductor memory device, e.g., a read-only memory device in a computer such as a solid-state drive (SSD)), and (ii) writable storage media on which changeable information may be stored (e.g., a floppy disk in a diskette drive or hard disk drive, or any type of solid-state random-access semiconductor memory). Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the methods described herein, are embodiments of the present disclosure. In some embodiments, the methods described herein, or portions thereof, are performed by one or more application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other types of hardware implementations. In some other embodiments, the substrate processing and / or handling methods described herein are performed by a combination of software routines, ASIC(s), FPGAs, and / or other types of hardware implementations. One or more system controllers 138 may be used with one or any combination of the various modular polishing systems described herein and / or with individual polishing modules thereof.

[0036]

[0040] 2 is an exemplary cross-sectional view illustrating the substrate support assembly 101. The substrate support assembly 101 includes an ESC 103, an ESC base 105, a facility plate 107, an insulator plate 109, a ground plate 111, and an edge ring 209.

[0037]

[0041] The chucking electrode 126 in the ESC 103 provides a chucking force when a voltage is applied to the chucking electrode and there is a voltage difference between the substrate 124 and the ESC chucking electrode 126. To obtain the chucking force, the substrate undersurface 203 must be in contact with the ESC support surface 130.

[0038]

[0042] The support surface 130 includes the upper surface of the ESC 103 and the tops of a number of posts 207 disposed within a backside gas cavity 205 of the ESC 103. The cavity 205 may be sealed or partially sealed from the processing region 110 (FIG. 1) by the support surface 130 and the substrate underside 203 when chucked via the chucking electrode 126.

[0039]

[0043] The backside gas cavity can be supplied with gas and evacuated through a backside gas conduit 221. When the cavity 205 is filled with backside gas, it further facilitates thermal energy transfer between the ESC 103 and the substrate 124. The backside gas supplied by the backside gas conduit passes through a porous plug 201. In some embodiments, the porous plug is disposed in the insulator plate 109.

[0040]

[0044] FIG. 3 illustrates a plug 201 for delivering backside gas to a substrate disposed on the ESC 103 of the substrate support assembly 101. The plug 201 is configured to reduce backside gas supply and pump-out times when using gases with atomic masses greater than that of helium, such as argon or other inert gases. The plug 201 exhibits a fluid flow rate that depends on the porosity of the material used to fabricate the plug 201. In some embodiments, the plug 201 is made of a cross-linked polystyrene material with uniform porosity. In some embodiments, the plug 201 material has a dielectric constant of about 2 to about 3, e.g., about 2.5. In one embodiment, the porosity of the plug 201 is a function of the grit size of the material used to fabricate the plug 201. In one embodiment, the grit size of the plug is about 50 μm to about 200 μm, e.g., about 100 μm to about 150 μm, e.g., about 115 μm to about 130 μm. The grit size selected can affect the porosity of the plug 201. In one embodiment, a single grit size is used to fabricate the plug 201. In this embodiment, the porosity of the plug 201 is substantially uniform. In another embodiment, multiple grit sizes can be used to fabricate the plug 201. In this embodiment, the porosity of the plug 201 is uniform or non-uniform, depending on the distribution of material of different grit sizes within the plug 201.

[0041]

[0045] The plug 201 has a top section 303 and a bottom section 307. The top section 303 has a top diameter 321, a top axial length 305, a top cross-sectional area, and a top volume. The bottom section 307 has a bottom diameter 319, a bottom axial length 309, a bottom cross-sectional area, and a bottom volume.

[0042]

[0046] The upper diameter 321 is about 0.45 inches to about 0.55 inches. The upper axial length 305 is about 1 inch to about 1.3 inches. The upper cross-sectional area is about 0.15 to about 0.2 square inches. The upper volume is about 0.2 to about 0.3 cubic inches.

[0043]

[0047] The bottom diameter 319 is about 0.35 inches to about 0.45 inches. The bottom axial length 309 is about 0.1 inches to about 0.3 inches. The bottom cross-sectional area is about 0.1 to about 0.2 square inches. The bottom volume is about 0.02 to about 0.04 cubic inches.

[0044]

[0048] Top diameter 321 is larger than bottom diameter 319. Top axial length 305 is larger than bottom axial length 309. The cross-sectional area of ​​bottom section 307 is smaller than the cross-sectional area of ​​top section 303. Top section 303 and bottom section 307 have a volume ratio of about 2 to about 12, such as about 4 to about 10, such as about 7 to about 7.4. Top axial length 305 and bottom axial length 309 have a ratio of about 2 to about 10, such as about 4 to about 6, such as about 5.05 to about 5.07. In this embodiment, plug 201 allows more backside gas (e.g., argon) to flow through plug 201, resulting in an increased argon flow rate and ultimately increased throughput.

[0045]

[0049] Alternatively, the porosity, diameter, volume ratio, and axial length of the plug 201 can be modified to improve backside gas flow.

[0046]

[0050] The plug 201 is disposed within the insulator plate 109 having an upper plug section face 331 opposite the bottom section 307. The upper section 303 is disposed adjacent to or in contact with the bottom of the facilities plate 107. The upper surface of the insulator plate 109, the lower surface of the facilities plate 107, and the upper plug section face 331 are disposed substantially coplanar. The plug 201 is at a junction with a backside gas conduit 330. The backside gas conduit may be a single central passage or may be a network of conduits that penetrate the facilities plate 107, the ESC base 105, and the ESC 103, supplying and exhausting backside gas to and from the substrate 124.

[0047]

[0051] The plug 201 is configured to allow the passage of gases but prevent arcing between the process region 110 and the ground plate 111 .

[0048]

[0052] An elastomeric seal 313 is disposed around the periphery of the upper plug section face 331. The seal 313 is disposed between the insulator plate 109 and the equipment plate 107. Alternatively, the seal 313 is a recess in the equipment plate 107. The seal 313 provides a gas seal at both high and low temperatures and is capable of sealing against atmospheric and sub-atmospheric pressures. In another embodiment, the plug 201 is disposed in or adjacent to the ESC base 105 and is configured to deliver gas through the plug to the backside of a substrate 124 disposed on the ESC 103.

[0049]

[0053] Although the leak rate of helium is typically greater than that of argon, by utilizing plug 201 to deliver argon to the backside of the substrate, the leak rate of argon can be significantly increased through the plug, achieving an argon gas delivery rate comparable to or greater than the leak rate of helium. Thus, by utilizing plug 201, the time required for argon backside gas delivery can be reduced, resulting in increased throughput.

[0050]

[0054] The plug described herein allows for the replacement of helium with argon as the backside gas. Helium is a conventional backside gas that can be achieved at high flow rates through other conventional plugs due to its small molecular size. Helium is expensive, which adds additional cost to semiconductor manufacturing. Argon is incompatible with conventional backside gas plugs due to its large molecular size.

[0051]

[0055] In addition to the plug, embodiments described herein include a method for chucking a substrate. To minimize the detrimental effects of suddenly applying a high voltage to the chuck electrode, which imparts a large force to the substrate, the present disclosure provides a two-stage "soft" chucking process. That is, instead of applying a high voltage for chucking nearly instantaneously, the voltage is increased in two stages, ramping from a low set point to a high set point. While the exemplary embodiments described herein describe a two-stage chucking process, other embodiments may be three or more stages.

[0052]

[0056] A sudden increase in chucking force can damage the backside of the substrate. Typically, a substrate is first placed at room temperature before processing. In some processes, a moderate to relatively high chucking voltage, such as 2000 V, is applied to the substrate by an electrostatic chuck (ESC). During some processes, contact with a cooled ESC reduces the substrate temperature from room temperature to values ​​as low as −90°C. A significant temperature drop of a chucked substrate by an electrostatic chuck maintained at a cryogenic temperature (e.g., −90°C or lower) can cause the substrate to contract radially. In some cases, the substrate temperature may not fully stabilize or equilibrate to the ESC temperature after the chucking process is complete and before the subsequent substrate processing step begins. This can result in damage to the substrate and / or the surface on which the substrate rests, and increased particle shedding from the backside of the substrate.

[0053]

[0057] However, the inventors have found that if a low chucking voltage is applied in a first stage, the substrate temperature is allowed to stabilize or equilibrate, and then a higher chucking voltage is applied in a second stage, fewer particles are generated on the backside of the substrate while the temperature of the substrate is equilibrating during this first stage because a lower chucking voltage, and therefore a lower chucking force, is applied to the substrate in the first stage. The lower force applied while the temperature of the substrate is rapidly changing from room temperature to the temperature of the electrostatic chuck reduces the contact stress interaction between the backside of the substrate and the top surface of the electrostatic chuck, minimizing the amount of physical damage to the substrate or the ESC surface on which the substrate rests.

[0054]

[0058] The inventors have found that applying a relatively low first-stage chucking voltage, such as about 700 V to about 900 V, achieves temperature stabilization of about −70° C. to about −100° C. in about 20 to about 30 seconds. Once the substrate temperature is stabilized, a higher second-stage chucking voltage, such as about 1900 V to about 2000 V, can be applied to the chucking electrode to complete the chucking process and increase thermal contact between the backside of the substrate and the top surface of the ESC. Because the temperature difference between the backside of the substrate and the top surface of the ESC during the second stage is relatively small, relative movement between the backside of the substrate and the top surface of the ESC due to thermal mismatch is small. For example, the temperature difference between the ESC and the substrate is less than 20° C., or less than 10° C., or less than 5° C., or even less than 3° C.

[0055]

[0059] It should be understood that the particular voltage applied in each stage may vary, for example, in other embodiments the voltage of the first stage may be other than 800V and the voltage of the second stage may be other than 2000V.

[0056]

[0060] Preliminary testing has shown that the use of a two-stage soft chucking process with a 25 second first stage interval has no measurable effect on the amount of helium or argon gas leaking from the backside of a substrate at a set backside gas pressure compared to a single-stage chucking process. Thus, the use of the two-stage chucking process described herein does not result in increased backside gas leakage compared to a single-stage chucking process.

[0057]

[0061] The results show an analysis of the number of particles emitted from the backside of the substrate for two embodiments. In the first embodiment, the backside gas applied to the substrate is helium. In this embodiment, when a 30 second time interval was used for the first stage duration, the number of particles greater than 2 micrometers was reduced from approximately 30,000 for the baseline (or one-stage) chucking process to approximately 19,000 for the two-stage chucking process. This resulted in a reduction of up to 34% in the number of particles emitted from the backside of the substrate.

[0058]

[0062] In a second embodiment, the backside gas applied to the substrate is argon. In this embodiment, the number of particles greater than 2 micrometers was reduced from approximately 30,000 for a baseline chucking process to approximately 5,000 for a two-stage chucking process using a 30-second time interval for the first stage duration. This resulted in an up to 83% reduction in the number of particles emitted from the substrate backside.

[0059]

[0063] 4 illustrates a chucking process 400 performed by controller 138 to chucking substrate 124 with chucking electrode 126 in ESC 103 (FIG. 1). Memory 138B includes instructions for implementing and implementing process 400.

[0060]

[0064] In step 401, the substrate 124 is placed on the ESC 103 in the process chamber 100. The process chamber 100 may be under vacuum. The ESC 103 has an ESC temperature less than 0°C. For example, the temperature of the ESC 103 is less than -10°C. For example, the temperature of the ESC 103 is less than -50°C. For example, the temperature of the ESC 103 is between about -80°C and about -100°C, e.g., about -90°C.

[0061]

[0065] In step 403, the ESC 103 applies a first voltage to the chucking electrode 126. The first voltage is about 700 V to about 900 V, for example, 800 V. The application of the first voltage to the chucking electrode 126 (FIG. 2) in the ESC 103 applies a force to the substrate 124.

[0062]

[0066] In step 405, a backside gas is flowed from the ESC 103 to the substrate underside 203 at a first pressure. The backside gas helps to equalize the temperature between the ESC 103 and the substrate 124. In some embodiments, the substrate 124 enters the chamber 100 at a substrate temperature of about 10° C. to about 40° C., e.g., about 15° C. to about 30° C., e.g., about 20° C. The backside gas flows into the cavity 205 (FIG. 2). The first pressure is about 10 Torr to about 20 Torr, e.g., about 12 Torr to about 16 Torr. The backside gas helps to equalize the substrate temperature and the ESC 103 temperature by increasing the transfer of thermal energy. In some embodiments, the backside gas is argon. In some embodiments, the backside gas is helium.

[0063]

[0067] In step 407, the substrate 124 is cooled by the ESC 103. Cooling is achieved by transferring thermal energy from the substrate to the ESC 103 via the backside gas. The substrate 124 is cooled from about 10°C to about -100°C, e.g., the substrate is cooled from about 25°C to -40°C. In some embodiments, the substrate is cooled from about -40°C to about -90°C in 10°C steps. For example, -40°C to -50°C, -50°C to -60°C, -60°C to -70°C, -70°C to -80°C, or -80°C to -90°C. The chucking time interval is about 20 seconds to about 30 seconds. Steps 403, 405, and 407 are performed within the chucking time interval. The steps can be performed in the order shown or simultaneously. During the chucking time interval, the substrate temperature is allowed to equalize to the ESC temperature. Uniformity includes having the substrate temperature within 100° C. of the ESC temperature. Uniformity includes having the substrate temperature within 10° C. of the ESC temperature. By having the substrate 124 uniformed at a first voltage and pressure, deflection of the substrate occurs at a low chucking force. The lower the chucking force, the less likely the substrate 124 will be damaged or generate particles from scratches.

[0064]

[0068] In step 409, a second voltage is applied to the chucking electrode 126 in the ESC 103. The second voltage is applied when the substrate temperature is less than 50° C. from the ESC temperature. For example, the second voltage is applied when the substrate is at approximately the same temperature as the ESC. In some embodiments, the backside gas pressure is also increased to a second pressure higher than the first pressure. The second voltage is applied after a chucking time interval. The second voltage is higher than the first voltage. The second voltage is applied after the substrate temperature has equalized to the temperature of the ESC. In some embodiments, the second voltage is about 1800 V to about 2200 V, e.g., 2000 V. In some embodiments, the change from the first voltage to the second voltage may be at a linear rate that continuously increases from the first voltage to the second voltage. In some embodiments, the second voltage is applied after about 25 seconds. The second pressure of the backside gas is from about 10 Torr to about 20 Torr, for example, from about 12 Torr to about 16 Torr.

[0065]

[0069] Process 400 can include additional intermediate steps where the voltage is increased by more than two increments. For example, process 300 can include four voltage increases. The voltage change between the first voltage and the second voltage can be a continuously varying voltage where the voltage is ramped from the first voltage to the second voltage by a linear slope (V / s).

[0066]

[0070] 5 illustrates a process 500 for dechucking a substrate 124 from the ESC 103. After processing the substrate 124, the process 500 is performed, which includes a two-stage soft dechucking process. Memory 138B contains instructions for implementing and implementing the process 500.

[0067]

[0071] In step 501, the backside gas flow and / or pressure to the cavity 205 (FIG. 2) is reduced. In some embodiments, the backside gas flow to the cavity 205 is stopped or evacuated. In some embodiments, the backside gas pressure is reduced from the second pressure to the first pressure described above. As the backside gas pressure is reduced, the rate of thermal energy transfer slows and the substrate temperature begins to increase.

[0068]

[0072] In step 503, the applied voltage is reduced. The applied voltage is about 1800V to 2200V, for example, 2000V. The applied voltage is reduced to a dechucking voltage. The dechucking voltage is about 700V to about 900V, for example, 800V. The dechucking voltage is applied by the chucking electrode 126 (FIG. 2) in the ESC 103.

[0069]

[0073] In step 505, the substrate 124 is allowed to equilibrate to the ambient chamber temperature during the dechucking interval. The dechucking interval is about 10 seconds to about 40 seconds, for example, about 12 seconds. In embodiments in which the backside gas pressure is reduced, the backside gas pressure may be reduced during the dechucking interval. For example, once the substrate temperature reaches about −30° C. to −50° C., the backside gas pressure is reduced from the second pressure to the first pressure. In some embodiments, the backside gas pressure is reduced from the second pressure to the first pressure in a time shorter than the dechucking interval. In some embodiments, the applied voltage is reduced to the dechucking voltage at the end of the dechucking interval.

[0070]

[0074] In step 507, the backside gas pressure is further reduced from the first pressure to less than the first pressure. In some embodiments, the backside gas is turned off or vented and no longer applies a force to the substrate.

[0071]

[0075] In step 509, the voltage is reduced again. In some embodiments, the voltage is reduced from the dechuck voltage to 0 V. In another embodiment, the voltage is reduced from the dechuck voltage to a non-zero voltage, for example, ±200 V. In yet another embodiment, the voltage is reduced from the dechuck voltage to a non-zero voltage, for example, ±50 V, to balance any residual charge on the wafer. After step 509, the substrate is no longer subjected to a chucking force and can be removed from the process chamber.

[0072]

[0076] As described above, applying a voltage to the substrate while maintaining uniform temperature and pressure can reduce damage to the substrate and the generation of contaminants.

[0073]

[0077] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof as determined by the following claims.

Claims

1. 1. A substrate support assembly comprising: an electrostatic chuck; an insulator plate; a porous plug disposed within the insulator plate, a first cylindrical section having a first volume and a first axial length; a second cylindrical section having a second volume and a second axial length; the first volume is greater than the second volume; the first axial length is greater than the second axial length; Porous plug and A substrate support assembly comprising:

2. The substrate support assembly of claim 1 , wherein the porous plug further comprises a porosity as a function of grit size of from about 50 μm to about 200 μm.

3. The substrate support assembly of claim 1 , wherein the first axial length is between 0.9 inches and 1.1 inches.

4. The substrate support assembly of claim 1 , wherein the first cylindrical section further comprises a first diameter, and the second cylindrical section further comprises a second diameter that is smaller than the first diameter.

5. The substrate support assembly of claim 4 , wherein the ratio of the first diameter to the second diameter is from about 1 to about 1.

4.

6. The substrate support assembly of claim 1 , wherein the first cylindrical section further comprises a first cross-sectional area, and the second cylindrical section further comprises a second cross-sectional area that is smaller than the first cross-sectional area.

7. The substrate support assembly of claim 6 , wherein a ratio of the first cross-sectional area to the second cross-sectional area is from about 1 to about 2.

8. The substrate support assembly of claim 1 , wherein a length ratio between the first axial length and the second axial length is from about 2 to about 10.

9. The substrate support assembly of claim 1 , wherein the volume ratio of the first volume to the second volume is from about 2 to about 12.

10. 1. A processing chamber comprising: one or more walls surrounding a process area; a substrate support assembly disposed in the process region, an electrostatic chuck disposed above an insulating plate; a porous plug disposed within the insulator plate, a porous material; a first cylindrical section having a first volume, a first diameter, and a first axial length; a second cylindrical section having a second volume smaller than the first volume, a second diameter smaller than the first diameter, and a second axial length smaller than the first axial length; a porous plug comprising a substrate support assembly including: A processing chamber comprising:

11. 11. The processing chamber of claim 10, wherein the porosity is a function of grit size, and the grit size is from about 50 [mu]m to about 200 [mu]m.

12. The processing chamber of claim 11 , wherein the porous plug is configured to allow the flow of an inert gas.

13. 13. The processing chamber of claim 12, wherein the inert gas is argon at a temperature below about -40°C.

14. 11. The processing chamber of claim 10, wherein the substrate support assembly further comprises a facilities plate disposed between the process region and the insulator plate, the porous plug being disposed within the insulator plate.

15. The processing chamber of claim 10 , wherein the material is cross-linked polystyrene.

16. 11. The processing chamber of claim 10, wherein the material has a dielectric constant of about 2 to about 3.

17. a volume ratio of the first cylindrical section to the second cylindrical section is from about 2 to about 12; the first cylindrical section is disposed between the second cylindrical section and the process region; a length ratio between the first axial length and the second axial length is from about 2 to about 10; The processing chamber of claim 10.

18. A porous plug comprising: a cross-linked polystyrene material having uniform porosity; a first cylindrical section having a first volume, a first diameter, and a first axial length; a second cylindrical section having a second volume smaller than the first volume, a second diameter smaller than the first diameter, and a second axial length smaller than the first axial length; Equipped with a volume ratio of the first cylindrical section to the second cylindrical section is from about 2 to about 12; the first cylindrical section is disposed between the second cylindrical section and a process region; a length ratio between the first axial length and the second axial length is from about 2 to about 10; Porous plug.

19. 20. The porous plug of claim 18, wherein the ratio of the first diameter to the second diameter is from about 1 to about 1.

4.

20. 20. The porous plug of claim 18, wherein the porosity is a function of grit size, and the grit size is from about 50 μm to about 200 μm.

21. 1. A method of chucking a substrate to a surface of an electrostatic chuck (ESC) in a processing chamber, comprising: applying a first voltage to a chucking electrode of the ESC during a chucking time interval; supplying an inert gas at a first pressure to a backside of the substrate during the chucking time interval; applying a second voltage to the chucking electrode after the chucking time interval, the second voltage being higher than the first voltage; supplying the inert gas to the backside of the substrate after the chucking time interval at a second pressure higher than the first pressure of the inert gas; A method comprising:

22. 22. The method of claim 21, wherein the inert gas is argon.

23. 22. The method of claim 21, further comprising equalizing the substrate temperature and the ESC temperature to within about 50° C. of each other before applying the second voltage, wherein the substrate temperature decreases during the chucking time interval.

24. 22. The method of claim 21, wherein the first voltage is from about 700V to about 900V.

25. 22. The method of claim 21, wherein the second voltage is from about 1900V to about 2100V.

26. 22. The method of claim 21, wherein the chucking time interval is from about 20 seconds to about 30 seconds.

27. 22. The method of claim 21, further comprising cooling the substrate to a first temperature during the chucking time interval.

28. 22. The method of claim 21, further comprising equalizing the substrate temperature and the ESC temperature during the chucking time interval.

29. 22. The method of claim 21, wherein the ESC is at a temperature lower than the temperature of the substrate.

30. 1. A method for dechucking a substrate from a surface of an electrostatic chuck (ESC) in a processing chamber, comprising: reducing a backside gas pressure on a lower surface of the substrate; After the pressure is reduced, reducing the voltage applied to the chuck electrode of the ESC to a dechucking voltage; increasing the substrate temperature during the dechucking interval; reducing the backside gas pressure after the dechucking interval; reducing the dechucking voltage; A method comprising:

31. 31. The method of claim 30, wherein the ESC has an ESC temperature maintained at a temperature below -10°C.

32. 31. The method of claim 30, wherein the dechucking interval is from about 10 seconds to about 40 seconds.

33. 31. The method of claim 30, wherein reducing the applied voltage to the dechucking voltage comprises reducing the applied voltage from between about 1900V and about 2100V to between about 700V and about 900V.

34. 31. The method of claim 30, wherein equalizing the substrate temperature comprises increasing the substrate temperature during the dechucking interval.

35. 1. A substrate processing chamber comprising: an electrostatic chuck (ESC) fluidly coupled to a cryogenic cooling system; A controller including a central processing unit (CPU), support circuits, and a non-transitory computer readable medium containing instructions for chucking a substrate, the instructions, when executed, performing: applying a first voltage to a chucking electrode of the ESC for a first time interval; applying an inert gas at a first pressure to the backside of the substrate for the first time interval; applying a second voltage higher than the first voltage to the chuck electrode for a second time interval after the first time interval; applying an inert gas at a second pressure to the backside of the substrate for the second time interval, the second amount of inert gas being less than the first amount of inert gas; and The controller and 1. A substrate processing chamber comprising:

36. The instructions may further include: reducing the backside gas pressure at the lower surface of the substrate; After reducing the pressure, reducing the voltage applied to the chuck electrode to a dechucking voltage; increasing the temperature of the substrate during a dechucking interval; reducing the backside gas pressure after the dechucking interval; decreasing the dechucking voltage after the dechucking interval.

36. The substrate processing chamber of claim 35,

37. 37. The substrate processing chamber of claim 36, wherein the inert gas is argon.

38. 36. The substrate processing chamber of claim 35, wherein the first voltage is from about 700V to about 900V.

39. 36. The substrate processing chamber of claim 35, wherein the first time interval is from about 20 seconds to about 40 seconds.

40. 36. The substrate processing chamber of claim 35, wherein the second time interval is greater than 2 seconds.

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